Integrated millimeter wave power amplifiers are typically limited to the hundreds of milliwatt output power range even when formed in wide bandgap (III-V) substrates. If greater output powers are desired, a circuit designer must then combine the output signals from multiple integrated power amplifiers using a suitable power combiner. Common power combiner architectures may be broadly classified into two main categories: 1) waveguide-based power combining; and 2) on-wafer/on-board power combining.
In a waveguide-based approach, a metallic waveguide network produces a power combiner having a low insertion loss since the enclosed metallic waveguides do not have any dielectric loss with the underlying substrate. However, even if MEMS micromachining techniques are used to form the metallic waveguides, design and production of suitable metallic waveguide-based power combiners is expensive and challenging.
A Wilkinson power combiner is an example of an on-board alternative to a waveguide-based architecture and is low cost in comparison to waveguide approaches. However, since the power combiner and divider network is integrated on the same wafer (or in lamination on a circuit board), thermal management is difficult.
Accordingly, there is a need in the art for improved power combiner architectures that provide the cost advantages of on-board solution yet achieve the low loss advantages of a waveguide-based approach.